Korean Connective Endings Made Easy: How to Link Sentences with -고, -아서/-어서, -지만, -(으)니까, -(으)면 and -는데

When you first start learning Korean, most of your sentences are short and simple: "I eat rice." "The weather is nice." "I am a student." That is a perfectly good start. Sooner or later, though, you will want to say more natural things, such as "The weather is nice, so let's go for a walk," or "I wanted to go, but I was busy." In English we do this with small words like and, so, but and because. Korean usually does it differently: instead of adding a separate word between two sentences, it attaches a special ending to the verb or adjective of the first sentence.

These endings are called connective endings (연결 어미). Learning the most common ones is one of the biggest steps from beginner to lower-intermediate Korean, because they appear in almost every conversation, drama scene and text message. In this guide we look at the essential connective endings one by one, explain how to attach them, compare those that are easy to confuse and finish with practical exercises.

How connective endings work

A Korean verb or adjective is made up of a stem and an ending. For example, in 먹다 (to eat), the stem is 먹- and -다 is the dictionary ending. In 가다 (to go), the stem is 가-. When you conjugate, you remove -다 and add a different ending. If you have already learned polite endings such as -아요/-어요, you have already done this.

Connective endings follow the same idea. You take the stem of the first verb or adjective, add a connective ending, and then continue with the second clause. The final verb of the sentence carries the politeness level and, in most cases, the tense.

Clause 1 (stem + connective ending)	Clause 2 (final verb with polite ending)	Meaning
밥을 먹고	학교에 가요.	I eat and (then) go to school.
비가 와서	집에 있어요.	It is raining, so I am staying home.
비싸지만	맛있어요.	It is expensive, but it is delicious.

Two things are worth noticing. First, the connective ending attaches directly to the stem, with no space. Second, the politeness of the whole sentence is decided by the last verb, so you do not need to make the first clause polite as well.

A quick reminder about stems

Many connective endings change shape depending on the stem. Three questions come up again and again:

• Does the stem end in a consonant or a vowel? Endings written with (으), such as -(으)면, add 으 after a consonant (먹으면) but not after a vowel (가면).
• Is the last vowel of the stem ㅏ or ㅗ? Endings such as -아서/-어서 use -아서 after ㅏ or ㅗ (가서, 와서) and -어서 after other vowels (먹어서, 읽어서).
• Is it a 하다 verb? Verbs and adjectives ending in 하다 usually become 해 (공부해서, 피곤해서).

If these rules feel familiar, that is because they are the same rules used for the polite present tense. Many learners find it helpful to think of -아서/-어서 as "the -아요/-어요 form without 요, plus 서".

-고: "and", "and then"

-고 is the simplest and most useful connective ending. It attaches to any verb or adjective stem without changes: 먹다 → 먹고, 가다 → 가고, 예쁘다 → 예쁘고.

It has two main uses:

• Listing: joining two facts of equal weight. 이 카페는 조용하고 커피가 맛있어요. (This café is quiet and the coffee is good.)
• Sequence: one action followed by another. 숙제를 하고 잘 거예요. (I will do my homework and then go to sleep.)

When you list facts with different subjects, -고 still works well: 형은 의사이고 동생은 학생이에요. (My older brother is a doctor and my younger sibling is a student.) For past events, the past tense usually appears only on the final verb: 어제 영화를 보고 저녁을 먹었어요. (Yesterday I watched a film and then had dinner.)

-아서/-어서: "so", "because", "and then"

-아서/-어서 is one of the most common ways to express a reason or cause. It also expresses a sequence where the first action is closely connected to the second.

Formation

Stem type	Rule	Examples
Last vowel ㅏ or ㅗ	-아서	가다 → 가서, 오다 → 와서, 좋다 → 좋아서
Other vowels	-어서	먹다 → 먹어서, 마시다 → 마셔서, 배우다 → 배워서
하다 verbs and adjectives	해서	공부하다 → 공부해서, 피곤하다 → 피곤해서
Nouns + 이다	-이라서 / -라서 (spoken) or -이어서 / -여서	학생이라서, 친구라서

Use 1: reason or cause

배가 고파서 라면을 먹었어요. (I was hungry, so I ate ramyeon.)
길이 막혀서 늦었어요. (The roads were jammed, so I was late.)
만나서 반가워요. (Nice to meet you, literally "Because we met, I am glad.")

That last phrase is one you may already know. It is a good reminder that -아서/-어서 is everywhere in everyday Korean.

Use 2: closely linked sequence

When the first action is necessary for the second, -아서/-어서 expresses "do A and then (with that) do B". For example, 친구를 만나서 카페에 갔어요 means "I met my friend and (together) we went to a café." Compare this with 친구를 만나고 카페에 갔어요, which simply lists two actions and could mean that you went to the café alone afterwards. Other examples include 의자에 앉아서 기다리세요 (Please sit on the chair and wait) and 사과를 씻어서 먹었어요 (I washed the apple and ate it).

Two important restrictions

• No past tense on the first clause: say 늦어서 미안해요, not 늦었어서. The final verb shows the tense.
• Not used with commands or suggestions: you should not say 비가 와서 우산을 가져가세요 in careful speech. For reasons followed by a command or suggestion, use -(으)니까 instead.

-(으)니까: "because", "since" (often with commands and suggestions)

-(으)니까 also expresses a reason, but it feels more like the speaker is presenting a reason to justify what comes next. It is especially common before commands, requests and suggestions.

Formation

• After a vowel: -니까 → 가다 → 가니까, 바쁘다 → 바쁘니까
• After a consonant: -으니까 → 먹다 → 먹으니까, 많다 → 많으니까
• Stems ending in ㄹ drop the ㄹ: 살다 → 사니까, 멀다 → 머니까
• With nouns: 학생이니까, 친구니까

Examples

비가 오니까 우산을 가져가세요. (It is raining, so take an umbrella.)
시간이 없으니까 택시를 탑시다. (We have no time, so let's take a taxi.)
날씨가 좋으니까 산책할까요? (The weather is nice, so shall we go for a walk?)

Unlike -아서/-어서, -(으)니까 can be combined with the past tense: 어제 많이 잤으니까 오늘은 괜찮아요. (I slept a lot yesterday, so I am fine today.)

A second meaning: discovery

-(으)니까 can also mean "when I did A, I found that B." 집에 가니까 아무도 없었어요 means "When I got home, (I found that) nobody was there." This "discovery" use is very common in storytelling.

-아서/-어서 or -(으)니까?

These two are the most frequently confused connective endings for learners. The table below summarises the key differences.

Point	-아서/-어서	-(으)니까
Main feeling	Natural cause and effect	Speaker's reason or justification
Followed by commands or suggestions	Avoided	Common and natural
Past tense in first clause	Not used	Possible
Fixed polite expressions	만나서 반가워요, 늦어서 미안해요	Rarely used for apologies or thanks
Typical example	아파서 학교에 못 갔어요.	아프니까 오늘은 쉬세요.

A useful rule of thumb is this: if the sentence ends with "please do", "let's do" or "shall we", reach for -(으)니까. If you are apologising or thanking someone for a reason, use -아서/-어서.

-지만: "but"

-지만 is a straightforward way to express contrast. It attaches to any stem without change: 비싸다 → 비싸지만, 먹다 → 먹지만.

한국어는 어렵지만 재미있어요. (Korean is difficult, but it is fun.)
가고 싶지만 시간이 없어요. (I want to go, but I have no time.)

Unlike -아서/-어서, -지만 can take the past tense: 열심히 공부했지만 시험이 어려웠어요. (I studied hard, but the exam was difficult.) It is also used in polite set phrases such as 죄송하지만... (I am sorry, but...) and 실례지만... (Excuse me, but...), which are handy when you need to ask a stranger for help.

-(으)면: "if", "when"

-(으)면 expresses a condition. It can mean "if" for hypothetical situations or "when" for regular, repeated situations.

Formation

• After a vowel: -면 → 가다 → 가면, 싸다 → 싸면
• After a consonant: -으면 → 먹다 → 먹으면, 좋다 → 좋으면
• Stems ending in ㄹ: just add -면 → 살다 → 살면, 놀다 → 놀면

Examples

시간이 있으면 같이 가요. (If you have time, let's go together.)
봄이 되면 벚꽃이 피어요. (When spring comes, the cherry blossoms bloom.)
모르면 물어보세요. (If you do not know, please ask.)

-(으)면 also forms several very useful patterns. -(으)면 좋겠어요 means "I hope" or "it would be nice if": 내일 날씨가 좋으면 좋겠어요 (I hope the weather is nice tomorrow). -아도/-어도 되다 and -(으)면 안 되다 are used for permission and prohibition: 여기에서 사진을 찍으면 안 돼요 (You must not take photos here).

-는데 / -(으)ㄴ데: background, contrast and soft introductions

-는데 is one of the most flexible connective endings, and you will hear it constantly in Korean dramas and conversation. Its basic job is to set up background information before the main point.

Formation

Word type	Ending	Examples
Action verbs (present)	-는데	가는데, 먹는데
있다 / 없다	-는데	있는데, 맛있는데, 없는데
Adjectives after a vowel	-ㄴ데	예쁜데, 바쁜데
Adjectives after a consonant	-은데	좋은데, 작은데
Noun + 이다	-인데	학생인데, 주말인데
Past tense	-았는데 / -었는데	갔는데, 먹었는데

In everyday speech, many people use -는데 with adjectives as well, but the forms above are the standard ones and are a safe choice for learners.

Use 1: giving background

지금 시장에 가는데 뭐 필요한 거 있어요? (I am going to the market now. Is there anything you need?)
이 식당에 처음 왔는데 정말 맛있네요. (This is my first time at this restaurant, and it is really delicious.)

Use 2: mild contrast

-는데 can express contrast in a softer way than -지만: 키는 작은데 힘이 세요. (He is short, but he is strong.)

Use 3: softening a sentence

When -는데요 ends a sentence, it often sounds gentle and leaves room for the listener to respond. 저는 괜찮은데요... (I am fine, though...) can politely suggest that the speaker has a different opinion or is waiting for a reaction. This is why -는데요 is so common in polite conversation and customer service.

Two more useful endings: -(으)면서 and -(으)러

-(으)면서: "while"

-(으)면서 expresses two actions happening at the same time by the same person. 음악을 들으면서 공부해요 (I study while listening to music). 밥을 먹으면서 드라마를 봐요 (I watch a drama while eating). Note that 듣다 becomes 들- before a vowel-initial ending, because it is a ㄷ irregular verb.

-(으)러: "in order to" with movement verbs

-(으)러 expresses purpose and is followed by a verb of movement such as 가다, 오다 or 다니다. 친구를 만나러 명동에 가요 (I am going to Myeongdong to meet a friend). 한국어를 배우러 한국에 왔어요 (I came to Korea to learn Korean). If the second verb is not a movement verb, use -(으)려고 instead: 한국어를 배우려고 책을 샀어요 (I bought a book in order to learn Korean).

Summary table of essential connective endings

Ending	Main meaning	Example
-고	and, and then	씻고 자요.
-아서/-어서	so, because; and then (linked)	피곤해서 일찍 잤어요.
-(으)니까	because (with commands/suggestions); when I found	추우니까 문을 닫으세요.
-지만	but	작지만 편해요.
-(으)면	if, when	도착하면 연락하세요.
-는데 / -(으)ㄴ데	background, soft contrast	배고픈데 밥 먹을까요?
-(으)면서	while	걸으면서 이야기해요.
-(으)러	in order to (with movement)	책을 사러 서점에 가요.

Common mistakes and how to avoid them

• Adding tense to -아서/-어서: 어제 아팠어서 is a very common error. Say 어제 아파서 학교에 못 갔어요.
• Using -아서/-어서 before a command: instead of 바빠서 나중에 전화하세요, say 바쁘니까 나중에 전화하세요.
• Forgetting 으 after consonants: 먹면 should be 먹으면, and 작니까 should be 작으니까.
• Keeping ㄹ where it drops: 살으니까 should be 사니까, and 멀은데 should be 먼데.
• Using -(으)러 with non-movement verbs: 공부하러 책을 샀어요 sounds unnatural; use 공부하려고.
• Translating word by word: English "and" does not always become -고. "I met my friend and we ate together" is more natural with -아서/-어서 because the actions are linked: 친구를 만나서 같이 먹었어요.

How to practise connective endings

Connective endings become natural through repetition and real use. These methods work well for many learners.

• Join your old sentences: Take simple sentences from your notebook and connect them in pairs using different endings. "I am tired. I will rest." becomes 피곤해서 쉴 거예요 and also 피곤하니까 쉬세요.
• Write a daily diary in three lines: Each day, write three sentences about your day, each using a different connective ending.
• Listen for endings in dramas: While watching a Korean drama with Korean subtitles, pause when you hear -는데, -니까 or -아서 and repeat the line aloud.
• Practise one ending per week: Focus on a single ending for a week, using it as often as possible in messages, notes and speaking practice.
• Make contrast pairs: Write the same idea with -아서 and -(으)니까, or with -지만 and -는데, and note how the feeling changes.
• Ask a teacher or language partner to check: Mistakes with tense and commands are easy to miss on your own, so occasional feedback is very valuable.

Connective endings in a real conversation

Grammar rules are easier to remember when you see them working together. Here is a short, everyday conversation between two friends. Notice how almost every sentence uses at least one connective ending.

A: 어제 뭐 했어요? (What did you do yesterday?)
B: 친구를 만나서 영화를 봤어요. (I met a friend and we watched a film.)
A: 어땠어요? (How was it?)
B: 영화가 길었지만 재미있었어요. (The film was long, but it was fun.)
A: 저도 보고 싶은데 요즘 시간이 없어요. (I want to see it too, but I have no time these days.)
B: 이번 주말에 시간이 있으면 같이 가요. (If you have time this weekend, let's go together.)
A: 좋아요. 토요일에 일하고 일요일에는 쉬어요. (Great. I work on Saturday and rest on Sunday.)
B: 그럼 일요일에 봐요. 오전에는 사람이 적으니까 아침에 만나요. (Then let's meet on Sunday. There are fewer people in the morning, so let's meet early.)

Look at how each ending does a different job. -아서 links two connected actions (meeting a friend, then watching a film together). -지만 adds a clear contrast. -는데 introduces background softly before the main point. -(으)면 sets a condition, -고 lists two plans, and -(으)니까 gives a reason before a suggestion. Try reading the dialogue aloud several times, then change the details, such as the film, the day or the reason, to make your own version.

Four more endings worth knowing next

Once the core endings feel comfortable, these four are natural next steps. They are common in daily life and easy to combine with what you already know.

-거나: "or"

-거나 attaches to any stem without changes and offers alternatives. 주말에는 책을 읽거나 산책해요 (At the weekend I read or go for a walk). 커피를 마시거나 차를 마셔요 (I drink coffee or tea). For nouns, use the particle 이나/나 instead: 커피나 차.

-다가: "while doing A, (then) B"

-다가 shows that an action was in progress and then was interrupted or changed. 집에 가다가 편의점에 들렀어요 means "On my way home, I stopped by a convenience store." 공부하다가 잠들었어요 means "I fell asleep while studying." The key idea is a shift in the middle of an action, which is what makes it different from -(으)면서, where the two actions simply happen together.

-기 전에: "before"

-기 전에 attaches directly to the stem: 자기 전에 이를 닦아요 (I brush my teeth before going to bed). 한국에 가기 전에 한글을 배웠어요 (I learned Hangul before going to Korea). It does not change shape, which makes it very beginner-friendly.

-(으)ㄴ 후에: "after"

-(으)ㄴ 후에 means "after doing". Use -ㄴ 후에 after a vowel and -은 후에 after a consonant: 수업이 끝난 후에 친구를 만나요 (I meet my friend after class finishes), 밥을 먹은 후에 커피를 마셔요 (I drink coffee after eating). In conversation you will also hear -(으)ㄴ 다음에 with the same meaning.

Ending	Meaning	Changes with stem?	Example
-거나	or	No	쉬거나 운동해요.
-다가	while doing, then (shift)	No	걷다가 넘어졌어요.
-기 전에	before	No	먹기 전에 손을 씻어요.
-(으)ㄴ 후에	after	Yes (consonant/vowel)	운동한 후에 샤워해요.

Learning endings in small groups like this, and always with example sentences, is far more effective than memorising long lists. Choose one or two at a time, use them in your own sentences for a few days, and move on only when they start to come out naturally.

Frequently asked questions

How many connective endings are there in Korean?

There are many, and some are quite advanced or literary. However, a relatively small group, including the ones in this guide, covers a large share of everyday conversation. It is better to master these well before moving on to more complex endings.

Can I use more than one connective ending in a sentence?

Yes. Korean speakers often link three or more clauses: 학교가 끝나서 친구를 만나고 같이 밥을 먹었는데 정말 맛있었어요. However, very long chains can be hard to follow, so it is a good idea to keep your sentences to two or three clauses at first.

Is -아서/-어서 or -(으)니까 more polite?

Neither is more polite in itself, because politeness depends on the final verb. However, -아서/-어서 is preferred in apologies and expressions of thanks, such as 늦어서 죄송합니다, and using -(으)니까 there can sound like you are making an excuse.

What is the difference between -지만 and -는데?

-지만 expresses clear contrast, much like "but". -는데 is softer and broader: it can show contrast, but it can also simply provide background. When you want a clear "but", -지만 is the safer choice.

Do these endings work in formal writing?

Most of them do. -고, -지만, -(으)면 and -아서/-어서 are used in both speech and writing. In formal writing, -(으)니까 is often replaced by -(으)므로 or -기 때문에, and the spoken -이라서 may become -이어서 or -이기 때문에.

Which ending should I learn first?

Start with -고 because it has no changes and is used everywhere. Then learn -아서/-어서 and -지만, followed by -(으)면 and -(으)니까. -는데 is very important, but its range of uses is easier to understand once you are comfortable with the others.

Final thoughts: from words to real conversation

Connective endings are the glue that turns separate Korean sentences into natural speech. With just a handful of them, you can explain reasons, express contrast, set conditions and tell simple stories about your day. Do not worry about mastering every nuance at once. Start by using -고, -아서/-어서 and -지만 in your own sentences, pay attention to how native speakers use -는데 and -(으)니까, and let your feel for the language grow little by little. Every sentence you connect brings you one step closer to speaking Korean the way it is really spoken.